1. Field of Invention
This invention relates to an electric connection box provided in a vehicle, such as an automobile or the like.
2. Description of Related Art
Heretofore, an electric connection box, in which an electric power distribution circuit is formed by stacking a plurality of bus bar boards, and in which fuses and relay switches are incorporated for distributing electric power from a common vehicle-mounted electric power source to various electronic units, has been generally known.
Further, in order to reduce a size of such electric connection box and to implement switching control, an electric connection box has been developed recently in which semiconductor switching devices such as field effect transistors (FETs) or the like are interposed between input and output terminals in lieu of the relay switches.
However, since these semiconductor switching devices have a relatively great calorific power, it is necessary to efficiently remove heat from the devices.
An electric connection box is disclosed in, for example, Japanese Laid-Open Patent Application No. 2001-319708 as one way for solving this problem. The electric connection box includes an electric power distribution section having an input terminal to be connected to an electric power source, output terminals, semiconductor switching devices interposed between the input and output terminals, and a bus bar circuit section, having metallic bus bars for forming a circuit and an insulation plate stacked on the bus bars, for connecting the respective output terminals of the electric power distribution section to vehicle-mounted loads. The electric power distribution section and bus bar circuit section are assembled in a common case with some of the bus bars in the bus bar circuit section being connected to the respective output terminals of the electric power distribution section.
In more detail, in the above-described electric connection box, the bus bars extend from the electric power distribution section and bus bar circuit section, respectively, and the extending ends are brought into contact with each other and are connected to each other so that the electric power distribution section is flush with the bus bar circuit section.
According to such an electric connection box, since the electric power distribution section including the semiconductor switching devices and the heat radiation member is independent of the bus bar board, it is possible to efficiently cool the respective semiconductor switching devices at a single, concentrated location.
In the electric connection box disclosed in the above-described Japanese Laid-Open Patent Application, it is necessary to incorporate all fuse elements on the bus bar board and to increase a size of the bus bar board itself according to the space required for the fuse elements. This is an inconvenience, which will be more significant as the number of the fuse elements increases. Since a plurality of fuse connection terminals (a pair of fuse terminals and tab terminals connected to the respective fuse terminals) must project from the bus bar board toward the fuse elements, this complicates the structure of the bus bar board.
Furthermore, since the bus bars at the electric power distribution section side are brought into contact with the bus bars at the bus bar board and are connected to each other by welding, the process is complex. Also, increase of connecting portions makes the structure complicated and lowers reliability of the connection.
An object of the present invention is to provide an electric connection box that can overcome the above-described problems.
In order to solve the above-described problems, the present invention is directed to an electric connection box, including: a case; a bus bar board including a plurality of bus bars, the bus bar board constituting a first electric power circuit and being accommodated in the case; a heat radiation member accommodated in the case and having a portion exposed outside the case; a plurality of heat radiation member-side bus bars connected to a first surface of the heat radiation member and constituting a second electric power circuit that connects to the first electric power circuit constituted by the bus bar board; and a plurality of switching devices, such as a semiconductor switching devices, mounted on the heat radiation member-side bus bars. Portions of the heat radiation member-side bus bars extend to form heat radiation member-side electrical component connection terminals. Portions of the bus bar board-side bus bars extend from the bus bar board near a position of the heat radiation member-side electrical component connection terminals and along a direction of the heat radiation member-side electrical component connection terminals to form bus bar board-side fuse connection terminals. Electrical components, such as fuses, are bridged between the heat radiation member-side electrical component connection terminals and the bus bar board-side electrical component connection terminals.
This structure according to the present invention can concentratedly and efficiently cool the plural switching devices by the heat radiation member, since the heat radiation member-side bus bars are connected to a surface of the common heat radiation member and the plural switching devices are mounted on the surface of the heat radiation member. Since the heat radiation member-side bus bars extend to form the heat radiation member side electrical component connection terminals, such as fuse connection terminals, and the electrical components elements, such as fuses, are bridged between the heat radiation member-side electrical components connection terminals and the bus bar board-side electrical component connection terminals, it is possible to reduce the occupying space of the bus bar board itself. It is also possible to reduce the number of the electrical component connection terminals that project from the bus bar board, since the output terminal bus bars constitute the electrical component connection terminals, thereby simplifying a structure of the bus bar board.
Since the heat radiation member-side bus bars are electrically connected through electrical components, such as fuse elements, to the bus bar board-side bus bars (that is, the fuse elements or other electrical components serve as connectors), the number of connecting portions can be decreased, and thus the structure can be simplified in comparison with a conventional abutment connection of the bus bars at the bus bar board side and at the heat radiation side in addition to an arrangement of the fuse elements or other electrical components.
In more detail, electrical component-fitting portions into which the electrical components can be inserted from the outside are provided in the case, and each electrical component terminal of the electrical components (such as fuse elements, for example) inserted into the electrical component-fitting portions is connected to the heat radiation member-side electrical component connection terminal and the bus bar board-side electrical component connection terminal to electrically interconnect the heat radiation member-side bus bars and the bus bar board-side bus bars. A simple work of inserting a fuse element or other electrical component into an electrical component-fitting portion can electrically interconnect the heat radiation member-side bus bar and the bus bar board-side bus bar at the same time as assembling the fuse element or other electrical component.
The heat radiation member may be disposed so that an end surface of the heat radiation member is disposed substantially in parallel with an end surface of the bus bar board, and the plurality of bus bar board-side electrical component connection terminals are parallel to the heat radiation member-side electrical component connection terminals. Consequently, it is possible to interpose the fuse elements or other electrical components between the heat radiation member-side bus bars and the bus bar board-side bus bars with a compact structure.
Furthermore, the heat radiation member can be secured to the case so that a surface of the heat radiation member is substantially perpendicular to the bus bar board. This arrangement can reduce the space occupied by the whole electric connection box in comparison with a conventional structure in which the heat radiation member is flush with the bus bar board.
It is not necessary to interconnect all of the heat radiation member-side bus bars and bus bar board-side bus bars by the fuse elements or other electrical components. One or more of them may be directly brought into contact with each other and connected to each other in a conventional manner.
In the present invention, the electric power circuit at the heat radiation member side may have various structures. Preferably, the heat radiation member-side bus bars include input terminal bus bars and output terminal bus bars, end portions of at least some of the output terminal bus bars constituting the heat radiation side electrical component connection terminals. Switching devices, such as semiconductor switching devices, are bridged between the input terminal bus bars and the output terminal bus bars, and electric power is supplied from the input terminal bus bars to the output terminal bus bars when the switching devices are placed in an ON state. This construction can actuate an ON-OFF operation for electric power supply to the respective output terminal bus bars by using the respective switching devices at the same time, and can ensure safety of electric power supply to the electric loads by interposing the fuse elements or other electrical components between the output terminal bus bars and the bus bar board side bus bars.
In this case, a plurality of the output terminal bus bars are preferably arranged along the heat radiation member, with end portions of the output terminal bus bars extending beyond the end surface of the heat radiation member to form the heat radiation member-side electrical component connection terminals. The input terminal bus bars include switching device mounting portions, and the switching devices are bridged between the switching device mounting portions and the output terminal bus bars. This construction can interpose the fuse elements or other electrical components between the plural output terminal bus bars and the bus bar board-side bus bars in a compact structure.
In the electric connection box of the present invention, a control circuit board for controlling driving of the switching devices is preferably provided facing the rear surface of the heat radiation member. This construction can arrange the control circuit board in a compact manner by using the space behind the heat radiation member and can effectively protect the control circuit board from any objects outside the case.
Board connection terminals that stand upright from a surface of the heat radiation member may include bent-up portions of the heat radiation member-side bus bars on which the switching devices are mounted, and the control circuit board may be connected to the board connection terminals. This construction can electrically interconnect the switching devices and control circuit board by merely bending up the portions of the bus bars for forming the unit.